1. Field of the Invention
The present invention relates to a wiring structure in a driving circuit of a liquid crystal panel having a plurality of pixels disposed in a lattice shape therein. In particular, the present invention relates to a liquid crystal panel capable of efficiently achieving a prevention of display unevenness, while coping with a request of slimmed border in a display apparatus using the liquid crystal panel.
2. Description of Related Art
A display apparatus using a liquid crystal panel displays an image by allowing contrast to differ for each different position in the liquid crystal panel. Representation of the contrast is achieved by adjusting a transmission amount of light from a light source installed behind the liquid crystal panel at each position. Adjusting of the transmission amount of light is achieved by operating an alignment direction of liquid crystal molecules in a liquid crystal layer for each different position in the liquid crystal panel which holds the liquid crystal layer between polarizing substrates whose polarization directions are perpendicular to each other. A color image is represented by a set of points having different colors and contrasts. The liquid crystal panel achieves a display of the color image by making a position corresponding to each point as a pixel, and adjusting the color and contrast (luminance) of red (R), green (G), and blue (B) for each pixel. In particular, a matrix type liquid crystal panel has a pixel region in which a plurality of pixels are arranged in a lattice shape. The liquid crystal panel achieves the display of the color image by adjusting the transmission amount of light from the light source for color, for each pixel of the pixel region.
One pixel in the matrix type liquid crystal panel includes a plurality of sub-pixels. The one pixel is formed by the sub-pixels of each of RGB colors. The one pixel may have a configuration including two sub-pixels for each color. In this case, the one pixel includes six sub-pixels. In the configuration in which the one pixel includes two sub-pixels for each color, even when a pixel defect occurs in one sub-pixel of two sub-pixels, it is possible to prevent the entire pixel from becoming the defected pixel by complementing the defect with the other pixel, and maintain a ratio of normal pixels at a high level. In addition, by allowing the transmission amount of light in two sub-pixels to differ from each other, it is possible to finely adjust intermediate gradation of the color or luminance of each pixel.
The operation of the alignment direction of liquid crystal molecules in the liquid crystal layer is performed by adjusting an electric field strength applied between electrodes facing each other with the liquid crystal layer interposed therebetween. In the matrix type liquid crystal panel, the electrodes are respectively formed at locations corresponding to the sub-pixels on two glass substrates, briefly, so as to be formed in a lattice shape, a liquid crystal material containing the liquid crystal molecules is sealed between the two glass substrates disposed to face a surface on a side in which the electrodes are formed, and the alignment direction of the liquid crystal molecules corresponding to each sub-pixel is operated by controlling a voltage applied to each electrode. Further, each electrode is made of a highly translucent conductive material. Furthermore, an alignment film for aligning the liquid crystal molecules is formed on a circuit including the electrodes on each glass substrate.
In addition, the glass substrate has wirings formed thereon of the conductive material to control the voltage applied to the electrodes of each sub-pixel. In the glass substrate, conductor wires are formed in a row direction and a column direction depending on the numbers of the sub-pixels in the row direction and the column direction, the electrodes of each sub-pixel are connected to the wirings in the row direction and the column direction one by one, respectively. The voltage applied to the electrodes of each sub-pixel is controlled by applying a control signal to the electrodes of each column for each one row.
Further, in an active matrix type liquid crystal panel, the electrodes of each sub-pixel are connected with a thin film transistor (TFT), and are provided with an auxiliary capacitor (added condenser). Thereby, it is possible to maintain a control voltage in each sub-pixel during transferring the control signal for applying a signal to the electrodes of each column, and improve display quality. In addition, by allowing the control voltage to the auxiliary capacitors of two sub-pixels to differ from each other, it is possible to provide a difference in a voltage applied to the respective sub-pixels, and finely adjust the intermediate gradation of each pixel.
Therefore, the wirings to each electrode, and wirings for a signal to apply the control voltage of each auxiliary capacitor are formed on the glass substrate. In the wirings for the auxiliary capacitors, a plurality of wirings arranged in the row direction are connected to stem wirings wired in the column direction on both sides outside the pixel region, the stem wirings are connected to a control unit for the auxiliary capacitor, and the control signal of a rectangular wave is output from the control unit.
The number of pixels in a recent liquid crystal panel is, for example in a case of full high-definition, 1920 in the row direction and 1080 in the column direction. When one pixel is formed by six sub-pixels including two sub-pixels for colors of RGB, the number of sub-pixels becomes 1920×1080×6, which is ten million or more. Accordingly, the wirings of the auxiliary capacitor of each sub-pixel becomes a vast number and distance. Thereby, a transfer rate of the control signal to each row is decreased, and it may be observed as display unevenness.
A decrease in the transfer rate of the control signal can be prevented by increasing a thickness of the stem wiring. However, in the display apparatus using the recent liquid crystal panel, increasing of size and thinning, as well as slimmed border are required. Increasing of the thickness of the stem wiring causes greater difficulty in slimmed border.
Therefore, in a conventional display apparatus, by providing a branch line in the wirings to the auxiliary capacitors, a rounding of the control signal of a rectangular wave is restrained, and further for grouping the control voltage to the respective auxiliary capacitors into a plurality of types, a transfer speed of the control signal is improved.